Various medical X-ray imaging apparatuses are used according to various purposes. For example, apparatus for dentistry includes a panorama X-ray imaging apparatus for imaging a dental arch and thereabout at the same time, a cephalo imaging for imaging an entire head of a patient for orthodontics, and an X-ray computed tomography (CT) imaging apparatus for imaging a part of a dental arch with an X-ray cone beam. Linear tomography imaging is also possible for a section of a dental arch.
For the various types of X-ray imaging apparatuses, various X-rays are used such as a long radiation field for panorama imaging or the like, a wide radiation field for cephalo imaging and a cone beam for CT imaging. Further, various sensors such as an X-ray film, an X-ray image intensifier, and a two dimensional sensor including a CCD sensor, a MOS sensor or the like are used for the apparatuses. The specifications of the X-ray source and the X-ray sensor and the rotation condition depend on the type of imaging.
For example, in panorama X-ray imaging, the positions of the X-ray source and the X-ray sensor are moved along a trajectory so that a narrow X-ray beam always radiates the dental arch in the normal direction and detects the beam with an X-ray film or an X-ray digital sensor. In X-ray CT imaging, for example, an X-ray beam radiates an object while an arm which holds an X-ray generator and an X-ray detector opposing to each other is rotated, and a projection of the beam is detected with a digital sensor.
It is conventional to modify an existing X-ray imaging apparatus to perform various types of imaging. For example, it is proposed to enable panorama imaging and linear tomography imaging by changing from an X-ray digital sensor cassette to an X-ray film and vice versa. In an X-ray panorama imaging apparatus described in Japanese patent laid open Publication JP-A H9-135829/1997, in order to decrease a change time and to shorten a time for X-ray tomography imaging for smooth running and acceleration of a medical process, in an X-ray panorama imaging apparatus described in JP-A H9-135829, an X-ray film cassette and a digital X-ray sensor cassette are held in the same cassette holder, and one of them is set at the central position, while the other is retracted. Thus, one of them can be set fast manually or automatically. However, as the structure of an X-ray detector becomes complicated, and an exclusive X-ray detector is required instead of an X-ray detector for a general film cassette. Then, in a panorama X-ray imaging apparatus proposed in Japanese patent laid open Publication JP-A H11-104127/1999, an apparatus for a film cassette is modified a little to use a digital sensor cassette. When a digital sensor cassette is set instead of a film cassette, an imaging mode for the digital sensor cassette is selected automatically, and imaging conditions for the mode are set. Then an imaging is performed by supplying control signals to the digital sensor cassette.
In the above-mentioned various dental X-ray imaging apparatuses, panorama (and cephalo) imaging apparatuses are used widely. When a dentist observes a panorama X-ray photograph obtained with a panorama imaging apparatus and wants to have a tomography image on a part of the panorama view, the tomography image can be obtained if an X-ray CT imaging apparatus is available. However, because an X-ray CT imaging apparatus is expensive, it is not always possible for the dentist to use an X-ray CT imaging apparatus. Therefore, it is desirable that a simple modification of a panorama imaging apparatus makes X-ray CT imaging possible. However, because the specifications of X-ray detector and X-ray sensor, imaging conditions and the like are different among imaging types, simple replacement of X-ray sensor is not sufficient to implement various types of imaging.